In parallel with the progress of technologies and the improvement of lifestyle, most electronic devices are improved with a remote control function. A remote-controllable electronic device is generally equipped with a remote control, which is configured to emit signals to be received by a sensor of the electronic device. Then, the electronic device is operated in response to the received signals. Therefore, what signals or the amount of the signals can be received by the sensor determines the remote controllability of the electronic device.
The remote control generally emits signals within a predetermined frequency band, such as infrared signals. The sensor is designed to respond substantially only to the signals within the predetermined frequency band. A conventional remote-controllable electronic device typically has a casing formed with a hole corresponding to the position of the sensor so that the sensor is allowed to receive light signals. Moreover, in order to improve the exterior appearance of the electronic device, the hole is generally integrated with a cover. In some cases, the cover is made of materials transparent to lights and designed with larger size to increase the signal-receivable range of the sensor. However, in such arrangement, the possibility of receiving non-remote control signals, i.e. signals not emitted by the remote control (noise), is accordingly increased. The influence of noise becomes serious when the noise is within the receivable range of the sensor. More seriously, the electronic device might malfunction due to the noise.
Therefore, it is desirable to provide a remote-controllable electronic device with a specified receiving range, which imposes lesser restriction on the design of exterior appearance.